How will you be able to show proof of income to a bank in order to get loans for a house?
i'd say bitcoins aren't an asset that banks will take seriously at this point for loan consideration, and they certainly don't have the policies in place. when the ETF gets listed, i'd imagine those are regulated securities that you could list as assets for this.
in terms of "income" from trading, tax returns cover it, like any other self employment.